added travis file

.travis.yml

@@ -0,0 +1,95 @@
+language: cpp
+
+dist: bionic
+
+compiler:
+  - gcc
+
+before_install:
+  - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+  - sudo apt-get update -qq
+
+before_script:
+  - mkdir build
+  - cd build
+  - cmake ..
+
+script: make && ./test/unit_tests
+
+matrix:
+  include:
+    - compiler: gcc
+      addons:
+        apt:
+          sources:
+            - sourceline: 'ppa:ubuntu-toolchain-r/test'
+          packages:
+            - g++-8
+      env:
+        - CXX=g++-8
+        - CC=gcc-8
+
+    - compiler: gcc
+      addons:
+        apt:
+          sources:
+            - sourceline: 'ppa:ubuntu-toolchain-r/test'
+          packages:
+            - g++-9
+      env:
+        - CXX=g++-9
+        - CC=gcc-9
+
+    - compiler: clang
+      addons:
+        apt:
+          sources:
+            - sourceline: 'ppa:ubuntu-toolchain-r/test'
+            - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-8 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
+          packages:
+            - clang-8
+            - g++-8
+      env:
+        - CXX=clang++-8
+        - CC=clang-8
+
+    - compiler: clang
+      addons:
+        apt:
+          sources:
+            - sourceline: 'ppa:ubuntu-toolchain-r/test'
+            - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-9 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
+          packages:
+            - clang-9
+            - g++-8
+      env:
+        - CXX=clang++-9
+        - CC=clang-9
+    - compiler: clang
+      addons:
+        apt:
+          sources:
+            - sourceline: 'ppa:ubuntu-toolchain-r/test'
+            - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-10 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
+          packages:
+            - clang-10
+            - g++-8
+      env:
+        - CXX=clang++-10
+        - CC=clang-10
+    - compiler: clang
+      addons:
+        apt:
+          sources:
+            - sourceline: 'ppa:ubuntu-toolchain-r/test'
+            - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-11 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
+          packages:
+            - clang-11
+            - g++-8
+      env:
+        - CXX=clang++-11
+        - CC=clang-11